U.S. Pat. No. 4,589,905 discloses herbicides and algicides which are 1-alkyl-5-cyano-1H-pyrazole-4-carboxamides. The compounds are prepared by a multi-step process which includes reacting an alkylhydrazine with an alkyl .alpha.-acetyl-.alpha.-(dimethylaminomethylene)acetate to produce a 5-methyl-1-alkyl-1H-pyrazole-4-carboxylic acid ester, followed by conversion of the 4-carboxyl and 5-methyl groups to carboxamide and cyano groups, respectively.
This invention concerns the synthesis of 5-cyano-4,5-dihydro-3,4-dicarboxypyrazoles which are intermediates for the herbicides and algicides of U.S. Pat. No. 4,589,905. The process of the invention produces the pyrazole intermediates in high yield and purity, while employing inexpensive starting materials. Thus, an object of the present invention is to provide an economical and efficient process for preparing certain substituted pyrazoles. A second object of the present invention is to provide new compounds; namely, 5-cyano-4,5-dihydro-3H-pyrazole-3,4-dicarboxylic acid dialkyl esters, which are useful intermediates.